Recently, in a work machine such as a hydraulic excavator of this kind, so-called hybrid-type construction machine using not only an engine but also a motor generator as a power source has been proposed for the purpose of energy saving (high fuel efficiency) or for the purpose of reducing the amount of exhaust gas (for example, carbon dioxide, nitrogen oxide, particulate substances, and the like) that is discharged from an engine and that has an impact on environments. When pump absorption power exceeds the output upper limit of the engine, the hybrid-type construction machinery provided with the motor generator of this kind sets the power increase speed of the engine at a predetermined value or smaller by correcting a difference between the pump absorption power and the output upper limit of the engine using the power of the motor generator.
As a conventional technique related to the hybrid-type construction machinery of this kind, disclosed is Patent Literature 1 in order to prevent exhaust gas having an impact on environments, in particular, black exhaust from being generated by avoiding a decrease in engine combustion efficiency. In Patent Literature 1, the output upper limit of the engine at which the power increase speed of the engine corresponds to a predetermined increase rate or smaller is calculated. When pump absorption power exceeds the output upper limit of the engine, a hydraulic pump or a motor generator is controlled so that the power increase speed of the engine corresponds to a predetermined value or smaller by suppressing the upper limit of the pump absorption power to the output upper limit of the engine. Accordingly, the power of the engine is prevented from being steeply increased.